The invention relates to a compensation circuit for driver circuits.
The signals of input/output pad cells (I/O pad cell) of an integrated circuit must have a defined, minimum signal edge steepness of the signals passing via the I/O pad cells depending on the specification and/or depending on the desired requirement. Owing to temperature, voltage and process fluctuations, it is, however, possible for more or less pronounced diffusions of the signal edge steepness to occur. Owing to these, driver circuits for I/O pad cells must be configured in such a way that minimum signal edge steepness can be guaranteed even in what is referred to as the xe2x80x9cworst casexe2x80x9d i.e. at a very high temperature and with the low supply voltage and xe2x80x9cslowxe2x80x9d process parameters.
Hitherto, driver circuits have been used for this which simultaneously fulfill all the abovementioned requirements. The resulting driver circuits are, however, overdimensioned for most temperature, voltage and process values, giving rise to an increased xe2x80x9cground supply bouncexe2x80x9d which can negatively influence the operational capability of the entire integrated circuit and in the worst case lead to malfunctions.
The present invention is therefore based on the object of disclosing a compensation circuit for driver circuits which ensure a defined minimum signal edge steepness of a signal in the case of I/O pad cells even under unfavorable conditions.
This object is achieved according to the invention by means of a compensation circuit for driver circuits having the features of patent claim 1.
Advantageous refinements and developments of the invention are the subject matter of the subclaims.
According to the invention, a digitally controlled compensation circuit or compensation unit (DCCU) is provided for this and is connected upstream of the driver circuit. This compensation unit according to the invention is composed essentially of four circuit parts: a current reference source, a current-comparison source, a comparator stage and a logic stage. The comparison unit is used to compensate temperature, voltage and process fluctuations in the driver circuit for the I/O pad cells. In this way, the signal edge steepness of the signals passing via these I/O pad cells is monitored and kept approximately constant over the abovementioned fluctuations. Furthermore, this can also permit a considerably reduced xe2x80x9cground supply bouncexe2x80x9d to be achieved.